JP2006015888A - Pneumatic tire for motorcycle, and tire rim assembly including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a motorcycle, and a tire rim assembly including the same, in which assembly and disassembly of a rim can be easily performed with good workability without damaging a tire. <P>SOLUTION: This pneumatic tire 14 for a motorcycle comprises a pair of stranded bead cores 20 having winding of ribbon members of small width comprising a plurality of bead wires of high tension steel arranged in parallel and coated with rubber. The tire rim assembly 10 comprises the pneumatic tire 14 for a motorcycle installed on an MT-type specialized deep bottom rim 12. Inner circumferential length Lc of the stranded bead core 20 and inner circumferential length Lr of the MT-type specialized deep bottom rim 12 at a height position H of bead seat reference diameter D are set to make a ratio Lc/Lr in a range of 1.006-1.020. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  More particularly, the present invention relates to a pneumatic tire for a motorcycle mounted on an MT type special deep bottom rim and a tire rim assembly having the same, and more particularly, includes a pneumatic tire for a motorcycle optimal for use in a motorcycle and the like. The present invention relates to a tire rim assembly.

  A tire rim assembly 70 (see FIG. 6) to which a pneumatic tire 74 for a motorcycle is attached is used for the motorcycle. For example, the bead core of the tire rim assembly 70 may be a hexagonal bead core 72 as shown in FIG. 7 or a cable bead core 76 as shown in FIG.

  The rim constituting the tire rim assembly is normally a wide MT-type deep rim, and various contrivances have been made in order to improve rim assembling property and rim unraveling property (see, for example, Patent Document 1).

By the way, among these MT type deep bottom rims, the MT type special deep bottom rim in which the cross-sectional shape in the tire radial direction of the rim well portion is substantially one arc, the workability of rim assembly and rim unwinding is remarkably inferior. In the pneumatic tire 74 for a motorcycle having a normal circumference, there is a problem that it is difficult to assemble and rim the rim without damaging the tire.
JP-A-6-278415

  In view of the above facts, the present invention provides a pneumatic tire for a motorcycle that can perform rim assembly and rim removal with good workability without damaging the tire, and a tire rim assembly having the same. Is an issue.

  The present inventor, even in the case of a deep bottom rim, in a normal MT type deep bottom rim 80 (see FIG. 4 for both) in which the cross-sectional shape of the rim well portion 78 in the tire radial direction is substantially U-shaped. When performing rim assembly and rim unwinding, the workability is not so bad, and the rim well 81 can be performed without damaging the tire, and the rim well 81 has a substantially circular arc cross-sectional shape in the tire radial direction. In the rim 82 (see FIG. 5), when rim assembly and rim unraveling were performed, the workability was remarkably inferior, and the cause of tire damage was intensively studied.

  And this inventor paid attention to the deformation | transformation which arises in a bead core at the time of rim | limb assembly | assembly and rim | limb unwinding.

  Further, due to the clearance between the rim and the bead portion, when the pneumatic tire 74 is unwound from the rim 80 as shown in FIG. 4, and from the MT type special deep bottom rim 82 as shown in FIG. It was speculated that the length by which the bead core B of the pneumatic tire 74 extends in the circumferential direction differs depending on whether the rim 74 is unwound.

  Then, it is assumed that the bead core portion BP that is in contact with the rim well portion is positioned on the rim 80 and the MT special deep bottom rim 82 at a position where the distance from the tire equatorial plane CL is the same a. As shown in FIG. 5, the height difference b between the height position of the bead seat reference diameter D (the height position of the rim flange surface) H and the bead core portion BP in the MT type special deep bottom rim 82 is as shown in FIG. As shown in FIG. 3, the rim 80 has been found to be smaller than the height difference b ′ between the height position H ′ of the bead sheet reference diameter D ′ and the bead core portion BP. As a result, when the bead core portion BQ facing the bead core portion BP exceeds the rim maximum diameter portion, the separation distance L between the bead core portions BP and BQ in the MT-type special deep bottom rim 82 is the separation between the bead core portions BP and BQ in the rim 80. It was found that it was larger than the distance L ′, and the above guess was correct.

  Therefore, the present inventor conducted intensive studies and repeated experiments. Then, if the bead core is easy to stretch and the inner circumference of the bead core does not satisfy certain requirements, it is found that it is almost impossible to assemble and rim the rim without damaging the pneumatic tire. Repeatedly, the present invention has been completed.

  The invention according to claim 1 has a pair of strand bead cores formed by winding a plurality of high-strength steel bead wires in parallel and winding a small ribbon material covered with rubber, and is attached to an MT type special deep bottom rim. In the pneumatic tire for motorcycles, the ratio Lc / Lr between the inner peripheral length Lc of the strand bead core and the inner peripheral length Lr of the MT-type special deep bottom rim at the height position of the bead seat reference diameter is 1.006. It is characterized by being in the range of ~ 1.020.

  Assuming that the expansion force (stretch resistance) of the strand bead core is 100%, the expansion force of the hexagonal bead core is 126% and the expansion force of the cable bead core is 134%. . Therefore, from the viewpoint of having the characteristic of easily extending in the circumferential direction, the strand bead core is more suitable than the hexagonal bead core or the cable bead core.

  The hexagonal bead core has a structure in which a single wire is wound continuously in a spiral shape along the outer shape of the bead core. Therefore, the bead core has a strong tensile strength in the circumferential direction and is suitable for use as it is. Depending on the characteristics of the rim, it is possible to remove one side of the tire bead into the well of the rim, and the other side of the rim. In the case of a rim that has a fairly long straight path between both sides when going over the flange, the strength of this bead tensile strength will be damaged, and the rim flange will get over if the bead part of the tire is not greatly deformed elliptically It is difficult to avoid failure such as deformation / damage of the bead part.

  The cable bead core has a structure in which a thin wire called a sheath wire is wound around a relatively strong loop wire called a core wire in a layered manner. Even in the case of this bead core, the circumferential direction of the loop wire There is a problem that the tensile strength is strong and it is difficult to detach the rim from the rim as in the case of the hexagonal bead core described above.

  On the other hand, the strand bead core has a structure formed by winding and laminating a small width ribbon material in which a plurality of rubber-coated high strength steels are juxtaposed in the width direction. Interlayer displacement in the circumferential direction is possible though a little. Accordingly, by controlling the inner circumferential length ratio between the bead core and the rim to a ratio within the predetermined range defined in the present invention, the workability of rim assembly / rim unwinding is good, and the tire bead portion during this work Occurrence of failures such as deformation / damage can be prevented. Furthermore, it is possible to secure an appropriate tightening force between the rim and the tire bead, and it is possible to prevent problems such as a rim slip during use and a bead failure due to excessive tightening.

  When Lc / Lr is less than 1.006, rim assembly / rim unwinding workability is remarkably inferior, and when Lc / Lr exceeds 1.20, the tire is easily detached from the rim.

  In the first aspect of the invention, the bead core is composed of a strand bead core and Lc / Lr is limited to the range of 1.006 to 1.020, so that the workability is good without damaging the tire. A pneumatic tire for a motorcycle that can perform rim assembly and rim unraveling can be realized.

  In addition, in the event of an abnormal situation in the event of an unexpected decrease in internal pressure, an appropriate code corresponding to each value of the bead core circumference should be taken into consideration when considering further safety against rim resistance. It is also effective to insert additional reinforcing means such as layers and suitable rubber layers under the bead core.

  The invention described in claim 2 includes an MT type special deep bottom rim and the pneumatic tire for a motorcycle according to claim 1 attached to the MT type special deep bottom rim.

  Thereby, it is possible to realize a tire rim assembly that can perform rim assembly and rim unwinding with good workability without damaging the tire.

  Since the present invention has the above-described configuration, it is possible to realize a pneumatic tire for a motorcycle that can perform rim assembly and rim removal with good workability without damaging the tire, and a tire rim assembly including the pneumatic tire. .

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. FIG. 1 is a tire radial direction cross-sectional view of a tire rim assembly 10 according to an embodiment of the present invention.

  The tire rim assembly 10 includes an MT type special deep bottom rim 12 and a motorcycle pneumatic tire 14 mounted on the MT type special deep bottom rim 12.

  As shown in FIG. 2, the pneumatic tire 14 for a motorcycle has a belt, a breaker (or cap), and a tread portion outside a crown portion of a carcass (casing) 15 extending in a toroidal shape. Also, the pneumatic tire 14 for a motorcycle has a pair of strand bead cores 20 formed of a small ribbon material 18 formed by covering a plurality of high-strength steel bead wires 16 in parallel with each other and forming a pair of bead portions 22. Have. The strand bead core 20 is formed by winding the ribbon material 18. In the present embodiment, the configuration of the strand bead core 20 is configured such that the bead wires 16 are arranged in four stages and four rows.

  The ratio Lc / Lr between the inner peripheral length Lc of the strand bead core 20 and the inner peripheral length Lr of the bead sheet at the height position H of the bead sheet reference diameter D is set in the range of 1.006 to 1.020. Yes.

  In order to assemble the pneumatic tire 14 to the MT type special deep bottom rim 12, as shown in FIG. 3, the MT type special deep bottom rim 12 is placed on a mounting table 26 to be substantially horizontal. Then, a part 22P of the lower bead portion of the pneumatic tire 14 is brought into contact with the curved wall surface of the rim well portion 28. As a result, the facing portion 22Q of the bead portion facing the portion 22P is positioned above the upper flange portion 30.

  And the pneumatic tire 14 is pressed so that this opposing part 22Q may move over the upper flange part 30 to the rim well part 28 side.

  In this way, by arranging the upper and lower bead portions 22 at the height positions of the bead seat reference diameter of the MT type special deep bottom rim 12, the pneumatic tire 14 is placed on the MT type special deep bottom rim 12. Assume that the tire rim assembly 10 is incorporated (see FIG. 1).

  Thus, in this embodiment, instead of a hexagonal bead core or a cable bead core, a strand formed by winding and laminating a small ribbon material 18 formed by juxtaposing a plurality of rubber-coated high strength steels in the width direction. Since the bead core 20 is used, the interlayer displacement in the circumferential direction can be slightly performed through the covering rubber between the layers. Accordingly, by setting Lc / Lr within the range of 1.006 to 1.020, the workability of rim assembly / rim unwinding is good, and the deformation / deformation of the bead portion 22 of the pneumatic tire 14 during this work / Failures such as damage can be prevented. Furthermore, it is possible to secure an appropriate tightening force between the MT-type special deep bottom rim 12 and the bead portion 22, and it is also possible to prevent problems such as bead failure due to rim sliding during use and excessive tightening. .

<Test example>
This inventor manufactured the pneumatic tire (pneumatic tire of Example 1) which made Lc / Lr 1.013 about the pneumatic tire 14 which concerns on the said embodiment. The rim assembly / rim unloading test was conducted on the MT type special deep bottom rim 12 to evaluate the rim assembly / rim unwinding workability and the tire damage.

  Various conditions such as the dimensions of the rim and the pneumatic tire are shown below.

Rim: MT 7.50-16 M / C, rim having a well shape of a single arc Rim diameter: 406 mm
Tire size: 240 / 50R16M / C (rim width is 7.5 inches)
Bead core: 4-stage, 4-row strand bead core Inner circumference of bead core: 1284 mm
Carcass: Nylon 2 Carcass angle: 90 ° to the tire equator
Belt: Steel spiral belt, substantially 0 ° to tire equator
The evaluation results are shown in Table 1.

また、本発明者は、実施例１の空気入りタイヤに比べ、Ｌｃ／Ｌｒをパラメータとして変化させた空気入りタイヤを製造した。すなわち、Ｌｃ／Ｌｒを１．００６とした空気入りタイヤ（実施例２の空気入りタイヤ）、Ｌｃ／Ｌｒを１．０２０とした空気入りタイヤ（実施例３の空気入りタイヤ）を製造した。そして、実施例１の空気入りタイヤと同様に、ＭＴ形特殊深底リム１２へのリム組み／リム解きの試験を行い、作業性、タイヤの損傷について評価した。評価結果を表１に併せて示す。

In addition, the inventor manufactured a pneumatic tire in which Lc / Lr was changed as a parameter compared to the pneumatic tire of Example 1. That is, a pneumatic tire (pneumatic tire of Example 2) with Lc / Lr of 1.006 and a pneumatic tire (pneumatic tire of Example 3) with Lc / Lr of 1.020 were manufactured. Then, similarly to the pneumatic tire of Example 1, the rim assembly / rim unraveling test on the MT type special deep bottom rim 12 was performed, and the workability and tire damage were evaluated. The evaluation results are also shown in Table 1.

  Further, the inventor of the present invention has a conventional pneumatic tire having a hexagonal bead core 72 and Lc / Lr of 1.005 (pneumatic tire of Conventional Example 1, see FIG. 7), a cable bead core 76, and Lc / Lr / Lr. For a conventional pneumatic tire having a Lr of 1.002 (pneumatic tire of conventional example 2; see FIG. 8), a rim assembly / rim unloading test was similarly performed to evaluate workability and tire damage. The evaluation results are also shown in Table 1. The rim widths of the pneumatic tires of the conventional examples 1 and 2 are both 6 inches.

  As can be seen from Table 1, in the pneumatic tires of Examples 1 to 3, the workability of rim assembly and rim unwinding was good, and the tire was not damaged. On the other hand, in the pneumatic tires of Conventional Examples 1 and 2 where Lc / Lr is less than 1.006, the workability of rim assembly and rim unwinding is remarkably inferior, and a large crack is generated in the bead portion of the tire.

  The embodiments of the present invention have been described with reference to the embodiments. However, the above embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Needless to say, the scope of rights of the present invention is not limited to the above embodiment.

1 is a tire radial direction cross-sectional view of a tire rim assembly according to an embodiment of the present invention. It is sectional drawing which shows the structure of the strand bead core of the tire rim assembly which concerns on one Embodiment of this invention. It is side surface sectional drawing which shows incorporating the pneumatic tire which concerns on one Embodiment of this invention into MT type special deep bottom rim. It is the typical partial side view seen from the tire equator side which shows the separation distance of the radial direction of the bead part at the time of incorporating a pneumatic tire in MT type deep bottom rim. It is the typical partial side view seen from the tire equator side which shows the separation distance of the radial direction of the bead part at the time of incorporating a pneumatic tire in MT type special deep bottom rim. It is a tire radial direction sectional view of the conventional tire rim assembly. It is typical sectional drawing which shows that a bead core is a hexagon bead core with the conventional pneumatic tire. It is typical sectional drawing which shows that a bead core is a cable bead core with the conventional pneumatic tire.

Explanation of symbols

10 Tire rim assembly 12 MT type special deep bottom rim 14 Pneumatic tire for motorcycle (pneumatic tire for motorcycle)
16 Bead wire 18 Ribbon material 20 Strand bead core

Claims (2)

In a pneumatic tire for a motorcycle having a pair of strand bead cores formed by winding a plurality of high-strength steel bead wires in parallel and winding a small ribbon material covered with rubber, and mounted on an MT type special deep bottom rim,
The ratio Lc / Lr between the inner peripheral length Lc of the strand bead core and the inner peripheral length Lr of the MT type special deep bottom rim at the height position of the bead sheet reference diameter is within a range of 1.006 to 1.020. A pneumatic tire for a motorcycle, characterized by being.   A tire rim assembly comprising an MT type special deep bottom rim and the pneumatic tire for a motorcycle according to claim 1 attached to the MT type special deep bottom rim.

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